/*!
 * Crypto-JS v1.1.0
 * http://code.google.com/p/crypto-js/
 * Copyright (c) 2009, Jeff Mott. All rights reserved.
 * http://code.google.com/p/crypto-js/wiki/License
 */
(function () {

// Shortcut
    var util = Crypto.util;

    Crypto.PBKDF2 = function (password, salt, keylen, options) {

        // Defaults
        var hasher = options && options.hasher || Crypto.SHA1,
            iterations = options && options.iterations || 1;

        // Pseudo-random function
        function PRF(password, salt) {
            return Crypto.HMAC(hasher, salt, password, {asBytes: true});
        }

        // Generate key
        var derivedKeyBytes = [],
            blockindex = 1;
        while (derivedKeyBytes.length < keylen) {

            var block = PRF(password, salt + util.bytesToString(
                    util.wordsToBytes([blockindex])));

            for (var u = block, i = 1; i < iterations; i++) {
                u = PRF(password, util.bytesToString(u));
                for (var j = 0; j < block.length; j++) block[j] ^= u[j];
            }

            derivedKeyBytes = derivedKeyBytes.concat(block);
            blockindex++;

        }

        // Truncate excess bytes
        derivedKeyBytes.length = keylen;

        return options && options.asBytes ? derivedKeyBytes :
            options && options.asString ? util.bytesToString(derivedKeyBytes) :
                util.bytesToHex(derivedKeyBytes);

    };

})();
